To me, it means waiting a little longer and savin a few more dollars to buy a part that built to last, not a part that is built to a price point. It doesn't mean that you need to build your rig to be massive from the get-go. Take a look at some of the truly well thought out and well built rigs that we've all wheeled with. There's nothing wrong with wheeling on 33's - just build your rig to run those 33's reliably and well. Personally, I'd rather have a properly built rig on 33's and never go any bigger (and occasionally winch through something or take a bypass) than have a bogger-built POS on 37's that only makes one wheeling trip in six because it's always broken.
There's nothing wrong with (Fraser I'm going to pick on you) upgrading to a long arm suspension and leaving your craptacular stock axles in place...if you're on 33's and you wheel in a manner that doesn't bend axles and snap axle shafts. There's nothing wrong with the long arm upgrade itself - there's only something wrong if you cheap out on the long arm so that you can also spend a little bit of money on an axle "upgrade" that isn't going to last either.
To me, "Do it once, do it right" means that you won't convince yourself that a half-arsed el-cheapo JB-weld upgrade is worth doing....you'll keep the stock parts in place until you have saved the money to upgrade them properly. It doesn't mean that you can't wheel until your rig is bombproof - it just means that you should wheel in a way that is realistic based on the limitations of your rig. Skinny pedal, wheel hop, "Just a little bit more bump", and the "Jeep Dance" are all great when used by folks that have "done it once, done it right".